A.S. Young, J.J. Mutugi, D.P. Kariuki, D. Lampard, A.C. Maritim, P.N. Ngumi, A. Linyonyi, B.L. Leitch, S.G. Ndungu, A.C. Lesan and S.K. Mining
Protozoology Division
National Veterinary Research Centre
Kenya Agricultural Research Institute
P.O. Box 32
Kikuyu, Kenya
The Nakuru East Coast Fever Project is a programme jointly conducted by the National Veterinary Research Centre, at Muguga, the Veterinary Laboratories, at Kabete, and the managements of eight large and medium-size farms in Nakuru District, Kenya. The objective in the initial phase of the project was to determine both the costs incurred on these farms for tick control and the effects of tick-borne diseases. The total cost of control and economic losses due to ticks and tick-borne diseases for the farms was estimated to be US$13.64 per animal (Young et al., in press).
It was agreed that a pilot scheme to introduce immunization against theileriosis should be undertaken on one of the farms, Marula Ranch, and the acaricide control should be altered, removing spraying totally. The known tick-borne disease problems on this farm were Corridor disease, caused by Theileria parva lawrencei infection derived from the large resident buffalo populations; East Coast fever, caused by T. p. parva infection, probably derived from neighbouring farms; anaplasmosis; babesiosis, caused by Babesia bigemina infection; and sweating sickness. Frequent dipping and spraying using coumaphos, (Asuntol, Bayer) or, more recently, diamide (Triatics, Cooper Animal Health) did not prevent 480 clinical cases of theileriosis (8.3% of the total population) and 100 cases of other tick-borne diseases (1.7%) in 1986. The farm's diagnosis of clinical tick-borne diseases was largely confirmed over a 6-month period. The reasons for this lack of control of tick-borne disease are reviewed by Ochanda et al. (1988). Deaths from tick-borne diseases had been reduced dramatically by the use of parvaquone (Clexon, Wellcome) for theileriosis treatment and imidocarb dipropionate (Imizol, Wellcome) for babesiosis and anaplasmosis treatment: in 1986 only 53 animals died from theileriosis and 6 from babesiosis or anaplasmosis.
In the experiment carried out on Marula Ranch, 101 European-Boran crossbred cattle (50 cows and 51 calves) were selected, bled for serology and weighed. Two additional groups of 20 cattle each (10 cows and 10 calves) were chosen for sprayed (diamide) weight controls and for infection controls. All cattle were kept on diamide application during the immunization period.
Theileria p. lawrencei and T. p. parva stocks from another district were chosen to immunize the cattle because local T. parva stocks were not available and because an objective of the experiment was to determine whether non-local stocks gave protection in this area. Mutugi et al. (1988) had shown that T. p. lawrencei stocks from the Mara area (Narok District) gave complete cross-immunity with T. p. lawrencei stocks from O1 Pejeta (Laikipia District); therefore it was decided to use Mara and Trans-Mara stocks. These were T. p. parva (Kilae) stabilate 187 and T. p. lawrencei (Mare III), which were diluted at 1:10 and 1:80, respectively, for infection. An inoculation of 1 ml of the combined stabilates was given either subcutaneously in front of the ear or on the shoulder. Injections of a short-acting formulation of oxytetracycline hydrochloride (Medamycin 100, Techamerica Group, USA) were given on days 0 and 4 after inoculation of stabilate at 10 mg/kg bodyweight. The total cost of this immunization (for drug and needles, etc.) was KShs30 (US$1.66) for a 300-kg animal.
Minimal clinical monitoring was undertaken. Twenty-one of 240 lymph node biopsy smears (8.8%) taken from days 15 to 27 after infection had low schizont parasitoses. The conditions during immunization were poor, with little grazing just before the long rains, and the cattle were in poor condition. Three calves died during the immunization of causes other than ECF. Nine percent of the animals had significant antibody titres to T. parva schizont antigen before the experiment, 99% after immunization. After the start of the long rains the condition of the immunized cattle improved rapidly.
The second phase of the experiment was to expose the immunized cattle to tick-borne disease challenge on the ranch. The objectives of the exposure were to determine the following:
a) the efficacy of the theileriosis immunization
b) the problems caused by other tick-borne diseases in the area
c) the efficacy of acaricidal ear tags on tick infestation on the ranch
d) whether these tags would reduce the tick-borne disease challenge
The acaricidal tags were applied to groups 1-4 on 28 April 1988 and the last acaricidal application was on 3 May 1988. The arrangement of the groups is shown in Table 1. Observations made on the exposed cattle included close clinical monitoring in the morning and evening, with rectal temperatures and lymph node and blood smear samples taken when necessary. A theilerial reactor was defined as an animal clinically sick from theileriosis that, if not treated, would probably die. These cases were treated with parvaquone and long-acting tetracycline (Terramycin LA, Pfizer).
Table 1. Experimental design showing numbers, tick control and other manipulations of cattle allocated to different groups
|
Groups |
Conventional acaricide |
Immunized cattle (no.) |
Control cattle (susceptible) |
Remarks |
|
|
Group 1 |
None
|
10 cows |
2 cows |
Weighed at monthly intervals
|
|
|
|
Acaricidal ear tag |
9 calves |
2 calves |
||
|
|
Type 1* |
|
|
||
|
Group 2 |
None
|
10 cows |
2 cows |
Weighed at monthly intervals
|
|
|
|
Acaricidal ear tag |
9 calves |
2 calves |
||
|
|
Type 2* |
|
|
||
|
Group 3 |
None
|
10 cows |
2 cows |
Weighed at monthly intervals
|
|
|
|
Acaricidal ear tag |
10 calves |
2 calves |
||
|
|
Type 3* |
|
|
||
|
Group 4 |
None
|
10 cows |
2 cows |
Weighed at monthly intervals
|
|
|
|
Acaricidal ear tag |
10 calves |
2 calves |
||
|
|
Type 4** |
|
|
||
|
Group 5 |
None
|
10 cows |
2 cows |
Weighed at monthly intervals
|
|
|
|
Controls, no ear tags |
9 calves |
2 calves |
||
|
Group 6 |
Diamide sprayed once a week
|
- |
10 cows |
Weighed at monthly intervals
|
|
|
|
Weight controls, no ear tags |
|
10 calves |
||
|
Group 7 |
None
|
- |
10 steers |
Added to the experiment after 2½ months exposure
|
|
|
|
No ear tags |
|
|
||
|
Group 8 |
None
|
- |
12 calves |
|
|
|
|
No ear tags, calves born during experiment |
|
|
||
* Acaricidal ear tag Types 1-3: Amitraz, Camco, U.K., monolithic tag 10 or 15% diamide.
** Acaricidal ear tag Type 4: Amitraz, Camco, U.K., liquid reservoir.
In addition, ticks infesting the 4 calves and 4 cows were counted on half the body at weekly intervals in groups 1-5 and group 7. Serum and haemotological samples were taken at monthly intervals or as necessary. Records of all interventions, such as treatments, were kept.
One hundred and fifty days after the exposure began only one immunized animal had died of acute babesiosis. The immunization experiment was thus considered a success, especially because the ranch management expected great problems from other tick-borne diseases.
The cattle had to be exposed in a low-challenge area for a month due to flooding in the high-challenge area where there is a resident buffalo population. The tick infestation was very low during the first month. On moving the cattle to the high-risk area, the tick infestation increased but was still considered low. However, the incidence of tick-borne disease became fairly high and complicated.
To summarize the results, 10 of the 20 (50%) control cattle developed clinical disease, probably caused by T. p. lawrencei, and required treatment, while only 1 of 97 (1%) of the immunized cattle became a theilerial reactor (perhaps from T. taurotragi infection).
A complication was the occurrence of a theilerial syndrome in many of the control and immunized cattle characterized by the presence of few macroschizonts, a transient febrile response and the presence of large piroplasms with veils and bars in erythrocytes. This parasite was tentatively identified as T. taurotragi. Anaemia was minimal. There is no cross-immunity between T. parva and T. taurotragi (Young et al., 1977). This parasite is being isolated for laboratory characterization. The individual groups were analysed for theilerial reactors and the results are shown in Table 2.
Table 2. The theileriosis reaction of immunized and control cattle under different tick control regimes
|
Group |
Immunized cattle |
Controls |
|
1 |
0/19 |
2/4 |
|
2 |
0/19 |
2/4 |
|
3 |
0/20 |
3/4 |
|
4 |
0/20 |
0/4 |
|
5 |
1/19 |
3/4 |
On 21 July 1988 an additional group of 10 steers was introduced without tick control and 4 have become theilerial reactors even though the ticks infesting these cattle were removed weekly and applied to a buffalo at Kabete for T. p. lawrencei isolation. Twelve calves were born during the exposure and 4 of these have become theilerial reactors. All theilerial reactors recovered following parvaquone treatment, except for one calf in group 8, which died of theileriosis. The acaricidal ear tags reduced the tick infestation considerably compared to untagged controls but did not prevent transmission of theileriosis, with the possible exception of group 4. In this group a new type of linear release tag with a liquid reservoir, containing permethrin, was used.
One of our greatest worries in this experiment was the possible effects of other tick-borne diseases, since the immunized cattle were probably susceptible to them. A number of transient low fever responses were recorded, which appeared to be due to T. taurotragi, Ehrlichia bovis, Ehrlichia (Cytoecetes) ondiri and Borrelia theileri infections, all transmitted by ticks but none, with the exception of Ondiri disease, being fatal to cattle.
Boophilus decoloratus infestations were detected only late in the exposure and no Anaplasma marginale infections were detected. One acute B. bigemina infection and one Borrelia theileri infection did occur, but no other Babesia infections were detected. No Amblyomma spp., vectors of Cowdria ruminantium and T. mutans, have been detected infesting cattle to date.
The following points should be stressed about this experiment.
a) Theileria parasites from the Narok District (e.g., T. p. lawrencei and T. p. parva) gave good protection to cattle immunized with them in Nakuru District, a result already anticipated from laboratory experiments (Mutugi et al., 1988).b) The problems with other tick-borne diseases have not been very large.
c) Acaricidal ear tags gave a good reduction in tick infestation and, in some cases, in tick-borne disease challenge.
d) The low tick infestation on cattle was undoubtedly due to intensive acaricide control practiced on the normal cattle population using the pastures. (The majority of the ticks were derived from wildlife, particularly buffalo and waterbuck, grazing the same pastures.) Reduction of tick control will mean that the tick population maintained by cattle could increase.
The ranch now intends to apply such immunization and tick control on a large scale, which is of great interest since they have a population of 465 dairy (Friesians) and 5291 beef (Boran, Boran/European breed crosses) cattle. Further monitoring will include a cost benefit analysis of the introduction of immunization and reduction of tick control.
ACKNOWLEDGEMENTS
We are grateful for the support of the participating farmers of the Nakuru East Coast Fever Project. Animal Agro Ltd. are thanked for supplying us with tetracyclines and ear tags.
REFERENCES
Mutugi, J.J., Young, A.S., Maritim, A.C., Ndungu, S.G., Stagg, D.A. Grootenhuis, J.G. and Leitch B.L. (1988). Immunization of cattle against theileriosis using varying doses of Theileria parva parva and Theileria parva lawrencei sporozoites and oxytetracycline treatments. International Journal for Parasitology 18: 453-461.
Ochanda, H., Young, A.S., Mumo, J., Mutugi, J.J. and Omwoyo, P.L. (1988). Effects of temperature on the rate of transmission of Theileria parva parva infection to cattle by its tick vector, Rhipicephalus appendiculatus. Parasitology 97:1-7.
Young, A.S., Grootenhuis, J.G., Kimber, C.D., Kanhai, G.K. and Stagg, D.A. (1977). Isolation of Theileria from eland (Taurotragus oryx) infective for cattle. Tropenmedizin und Parasitologie 18:185-194.
Young, A.S., Kariuki, D.P., Mutugi, J.J., Heath, D.L. and Long, R.C. (in press). Economic losses in cattle due to tick control and effects of tick-borne diseases on selected farms in Nakuru District, Kenya, and the benefits of introducing immunization against theileriosis. Preventive Veterinary Medicine.
